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1.
The Bajo Segura Basin is located in the eastern Betic Cordillera, at present connected with the Mediterranean Sea to the east. It has a complete stratigraphic record from the Tortonian to the Quaternary, which has been separated into six units bounded by unconformities. This paper is concerned with the northern edge of the basin, controlled by a major strike–slip fault (the Crevillente Fault Zone, CFZ), where the most complete stratigraphic successions are found. The results obtained (summarised below) are based on an integrated analysis of the sedimentary evolution and the subsidence-uplift movements. Unit I (Early Tortonian) is transgressive on the basin basement and is represented by ramp-type platform facies, organised in a shallowing-upward sequence related to tectonic uplift during the first stages of movement along the CFZ. Unit II (lower Late Tortonian) consists of shallow platform facies at bottom and pelagic basin facies at top, forming a deepening-upward sequence associated with tectonic subsidence due to sinistral motion along the CFZ. Unit III (middle Late Tortonian) is made up of exotic turbiditic facies related to a stage of uplift and erosion of the southern edge of the basin. Unit IV (upper Late Tortonian) consists of pelagic basin facies at bottom and shallow platform facies at top, defining a shallowing-upward sequence related to tectonic uplift during continued sinistral movement on the basin-bounding fault. Units V (latest Tortonian–Messinian) and VI (Pliocene–Pleistocene p.p.) consist of shallowing-upward sequences deposited during folding and uplift of the northern margin of the basin. No definitive evidence of any major eustatic sea-level fall, associated with the ‘Messinian salinity crisis’, has been recorded in the stratigraphic sections studied.  相似文献   

2.
The Messinian sediments of northeastern Tunisia were deposited under an active tectonic setting. They are organized in sequences indicating a transitional deposit from margin – littoral to lacustrine – continental facies. These series unconformably overlie the Serravallian–Tortonian silty clays packages, and are overlain by the transgressive Early Pliocene marl (Zanclean). The presence of evaporitic strata points out to the Messinian Salinity Crisis described in the peripheral basins of the western Mediterranean. The Messinian sedimentation was found to have been closely controlled by transtensive tectonics and differential subsidence at a large spatio-temporal scale. It is organized in sequences typical of a depositional environment controlled by eustatism, tectonic and maybe by climate changes. Despite the existence of some local specific sedimentological characteristics, our results corroborate previous findings that pointed out to the Messinian times as a singular period all around the Mediterranean Basin. Field and subsurface seismic profile data helped reconstructing either the sedimentary or tectonic unconformities existing between the studied Messinian series and older Neogene successions.  相似文献   

3.
Several gateways connected the Mediterranean with the Atlantic during the late Miocene but the timing of closure and therefore their role prior to and during the Messinian Salinity Crisis (5.97–5.33 Ma) is still under debate. The timing of closure of the Guadalhorce Corridor is especially disputed as the common lack of marine microfossils hampers precise age determination. Here we present new biostratigraphic age constraints on the sediments of the Ronda, Antequera and Arcos regions, which formed the northern part of the Guadalhorce Corridor. The general presence of Globorotalia menardii 4 in the youngest deep‐marine sediments of all three regions indicates a late Tortonian age, older than 7.51 Ma. We conclude that the Guadalhorce Corridor closed during the late Tortonian, well before the onset of the Messinian Salinity Crisis and that the late Tortonian tectonic uplift of the eastern Betics extended into the western Betics.  相似文献   

4.
Astronomical tuning of the Messinian pre‐salt succession in the Levant Basin allows for the first time the reconstruction of a detailed chronology of the Messinian salinity crisis (MSC) events in deep setting and their correlation with marginal records that supports the CIESM ( 2008 ) 3‐stage model. Our main conclusions are (1) MSC events were synchronous across marginal and deep basins, (2) MSC onset in deep basins occurred at 5.97 Ma, (3) only foraminifera‐barren, evaporite‐free shales accumulated in deep settings between 5.97 and 5.60 Ma, (4) deep evaporites (anhydrite and halite) deposition started later, at 5.60 Ma and (5) new and published 87Sr/86Sr data indicate that during all stages, evaporites precipitated from the same water body in all the Mediterranean sub‐basins. The wide synchrony of events and 87Sr/86Sr homogeneity implies inter‐sub‐basin connection during the whole MSC and is not compatible with large sea‐level fall and desiccation of the Mediterranean.  相似文献   

5.
The Central Ebro River Basin (NE Spain) is the most northern area of truly semi-arid Mediterranean climate in Europe and prehistoric human occupation there has been strongly influenced by this extreme environmental condition. Modern climate conditions single out this region due to the harsh environment, characterised by the highest absolute summer temperatures of the Ebro River Basin. The Bajo Aragón region (SE Ebro River Basin) was intensively populated during the Early Holocene (9400-8200 cal yr BP) but the settlements were abandoned abruptly at around 8200 cal yr BP. We propose that this “archaeological silence” was caused by the regional impact of the global abrupt 8.2 ka cold event. Available regional paleoclimate archives demonstrate the existence of an aridity crisis then that interrupted the humid Early Holocene. That environmental crisis would have forced hunter-gatherer groups from the Bajo Aragón to migrate to regions with more favourable conditions (i.e. more humid mountainous areas) and only return in the Neolithic. Coherently, archaeological sites persist during this crisis in the nearby Iberian Range (Maestrazgo) and the North Ebro River area (Pre-Pyrenean mountains and along the northwestern Ebro Basin).  相似文献   

6.
东昆仑阿拉克湖地区第四纪水系演化过程及其趋势   总被引：6，自引：0，他引：6  
根据第四系沉积物的沉积时代、沉积类型及盆山耦合与迁移规律,将东昆仑阿拉克湖地区第四纪水系变迁划分了4个阶段：早更新世小型内陆盆地无序水系阶段;中更新世冰川水系与东流水系阶段;晚更新世柴达木盆地内陆水系向南溯源侵蚀阶段;全新世黄河外泄水系形成与发展阶段。根据研究区及相邻地区黄河水系和柴达木盆地内陆水系的溯源侵蚀发展历史及趋势分析,认为研究区未来水系发展趋势不一定是加鲁河袭夺鄂陵湖、扎陵湖两湖及黄河水系,而可能是黄河加快下蚀作用和溯源侵蚀,鄂陵湖和扎陵湖将逐渐消失成为河流,黄河水系最终将袭夺柴达木内陆盆地水系。  相似文献   

7.
This study represents a preliminary investigation of the late Messinian subsurface Marsa Zouaghah Formation in the Western Libyan Offshore, Central Mediterranean Sea. The formation was deposited in three major environmental settings: (a) Marginal Sabkha; (b) Open Lagoon; and (c) Hypersaline Lagoon. The marginal sabkha and open lagoonal settings are locally interrupted by intertidal oolitic shoal deposits. The marginal sabkha facies is replaced in central parts of the Libyan offshore by a narrow zone of aeolian-fluvial facies, the distribution and thickness of which is entirely controlled by a local uplift, the Tripoli Nose'. The marginal sabkha facies broadly defines the late Messinian palaeoshoreline lying parallel to, and north of, the E-W Jifarah fault system which dominated the southern part of the Libyan offshore. This fades is, thus, interpreted as being structurally controlled by fault systems. The hypersaline lagoonal facies is developed in areas of relatively higher rates of subsidence than that of adjacent facies belts. It is therefore, related to restriction formed by continuous subsidence and evaporation. The Marsa Zouaghah Formation constitutes saltern evaporates deposited over a wide platform in sabkha and lagoonal settings, forming part of the 'basin-wide-evaporites' of the Mediterranean Basin deposited during the Messinian salinity crisis. The evaporites formed during a major relative sea-level fall within a subsiding basin situated on the northern continental margin of the African plate. Local, vertical and lateral variations in lithofacies and thickness within the Messinian deposits of the north-west Libyan offshore were controlled by contemporaneous strike-slip movements in addition to sea-level change.  相似文献   

8.
Overfilled incised valleys develop when the rate of sediment supply outpaces the rate of accommodation. An overfilled incised valley presents simple or compound valley-fill architecture, depending on the depth of the valley incision, compared with the height reached by the following sea-level rise.The Ventimiglia incised valley, exposed on the Ligurian coast, north-western Mediterranean margin, presents a spectacular example of compound incised-valley fill, developed in perennial “overfill” conditions. The valley was subaerially incised during the Messinian Salinity Crisis and rapidly flooded by the sea at the beginning of Pliocene, then filled by eleven coarse-grained Gilbert-type deltas during Early–Middle Pliocene time.The basal Messinian unconformity is locally paved with subaerial scree breccias and bioclastic shallow-marine sandstones, and blanketed by bathyal marls. These deposits record the lowstand, transgressive and early-highstand systems tracts of the first valley-fill sequence. The subsequent progradation of Gilbert-type deltas occurred in four stages, or depositional sequences, separated by transgressive marine-marl intervals. Within each depositional sequence, the deltaic bodies display offlapping architecture, recording falling shoreline trajectory, downward shifts in facies, and overall forced regression. The water depth and accommodation in the inundated coastal valley was gradually decreasing with time. The reduced accommodation allowed the youngest deltas to prograde out to the shelf edge, triggering mass collapses and subsequent filling into the newly created slump scars. Some of the deltas probably acted as “canyon-perched deltas” and supplied sediment to the deep-water slope and floor of the Ligurian Basin.The vertical stacking of Gilbert-type deltas is usually attributed, in tectonically active basins, to fault-related subsidence pulses. In Ventimiglia, the accommodation was created by high-frequency eustatic sea-level rises that, probably accompanied by climate controlled reductions in sediment supply, temporarily outpaced uplift, leading to the development of multiple cycles of infill.  相似文献   

9.
During the late Miocene, the Guadalquivir Basin and its satellite basin, the Ronda Basin, were under Atlantic cool-water influence. The aim of our study is to develop a sequence stratigraphic subdivision of the Ronda Basin fill and to provide models for the cool-water carbonates. The Upper Miocene of the Ronda Basin can be divided into three depositional sequences. Sequence 1 is early Tortonian, Sequence 2 late Tortonian to earliest Messinian, and Sequence 3 Messinian in age. The sediments were deposited in a ramp depositional system. Sequence 1 is dominated by conglomerates and marls. In Sequence 2 and Sequence 3, carbonate deposits dominate in the inner ramp whereas siliciclastics preferentially occur in the middle and outer ramp. Bryomol carbonate sediments occur in all sequences whereas rhodalgal carbonates are restricted to Sequence 3. In bays protected from siliciclastic influx, rhodalgal deposits formed under transgressive conditions. A bryomol factory occurs in zones of continuous siliciclastic supply. This distribution results from facies partitioning during the flooding of the Ronda Basin, which has a rugged and irregular relief. Embayments were protected from siliciclastic influx and provided regions with less hydraulic energy.  相似文献   

10.
The Yangtze, the longest river in Asia, was hypothesized to be assembled through a series of Cenozoic capture events, such as the reversal of Middle Yangtze River and the capture of Upper Yangtze River, but the history remains largely unknown. Here, we present new geomorphic observations in the structural context of the eastern Sichuan Basin, namely the Eastern Sichuan fold belt, and identify an important drainage divide along the “midline” of this arc-shape fold belt. Based on longitudinal profile analysis, we find that the river capture events more likely occurred in the syncline valleys of low-relief landscape. Our results yield a new perspective on Middle Yangtze River reversal, and we propose that the “midline” drainage divide, rather than the Three Gorges, was the starting site of Middle Yangtze River reversal. In this manner, the reversal could have been accomplished by a sequence of river reversal over range-parallel segments in syncline valleys with less impact on the pre-existing drainage system in eastern Sichuan Basin.  相似文献   

11.
This study describes the lithostratigraphic character of mid-Cenozoic (Oligocene-Pliocene) sequences in different parts of the northeastern Mediterranean area and offers a detailed stratigraphic correlation for this region. The sequences concerned are drawn from the Camardi area (south-central Anatolia), the Adana Basin, the Misis Mountains and the Kyrenia Range (northern Cyprus) and the submerged Florence Rise (west of Cyprus). The stratigraphic relationships identified here indicate the following: (a) Following the middle Eocene (Lutetian) regression there was uplift throughout the entire region; (b) Episodes of fluvial and lacustrine deposition in intramontane settings ensued in most of this region during the late Eocene/early Miocene interval; (c) Following a regionally extensive phase of tectonic compression, major marine transgression commenced in the late Oligocene in northern Cyprus and in the early Miocene in adjacent southern Turkey, with the exception of the Ecemi§ Fault Zone where continental deposition continued; (d) These Oligo-Miocene transgressive sequences comprise a broadly diachronous complex of both shallow and deeper marine facies, including reefal carbonates, littoral clastics, basinal shales and fan-turbidites; (e) Deeper marine Miocene facies persisted longer in the Misis area and in northern Cyprus; (f) A regional regression occurred throughout most of the area during the late Serravallian to Tortonian interval and is marked by the abrupt, locally discordant appearance of extensive shallow marine, deltaic and fluvial deposits; (g) Continued regression in the Messinian led to the formation of significant evaporite deposits in the western and southern parts of the region, but localized uplift of the Misis area is attested by the initial deformation of the Neogene rocks there and the absence of Messinian sediments from this area; (h) In the Pliocene there was extensive emergence of the northern parts of the region interrupted by brief marine incursions. The present-day drainage pattern was established at this time; (i) Marine conditions persisted longer in northern Cyprus, where emergence occurred only in the latest Pliocene.  相似文献   

12.
The signature of the Mediterranean Messinian Salinity Crisis (MSC) in the Paratethys has received wide attention because of the inferred changes in connectivity and base level. In this article, we present sequence stratigraphic interpretations on a seismic transect across the western part of the semi-isolated Late Miocene–Pliocene Dacic Basin (Eastern Paratethys, Romania), chronologically constrained by biostratigraphic field observations and well data. They reveal significant sea level changes during the middle Pontian that are coeval with the MSC. These changes were most likely transmitted to the western Dacic Basin from the downstream Black Sea and controlled by the sill height of the interconnecting gateway. During the middle Pontian lowstand of the western Dacian Basin, sedimentation continued in a remnant ∼300 m deep lake with a positive water balance. Our observations show that the evolution of semi-isolated sedimentary basins is strongly dependent on the communication with other depositional realms through its control on base level and sediment supply.  相似文献   

13.
The Late Miocene to Pleistocene evolution of the northwestern Iblean plateau (Sicily) is marked by a complex interplay of subaerial and submarine volcanism, subsidence and uplift, eustatic sea-level changes, and shallow-water carbonate and clay sedimentation. Volcanic activity occurred in distinct phases, differing drastically in volume, chemical composition, eruptive and depositional sites, and eruptive mechanisms. Six of the newly defined formations in the northwestern Iblean plateau are either entirely volcanic or contain significant amounts of volcanics. The eastern part of a shallow marine basin was filled completely by Late Pliocene tholeiitic lava flows (Militello Formation) that had advanced subaerially from the south–southeast. Lava deltas advanced southwestward on top of earlier pillow breccia debris flow deposits intertongued with soft Trubi marls and chalks. True submarine eruptions (Monte Caliella Formation) simultaneously produced densely packed pillow piles up to 250?m thick. Inferred water depths based on volcanologic and paleoecologic criteria of interbedded and overlying calcarenites agree well. Subsequent alkalic, more explosive Pleistocene volcanic eruptions (Poggio Vina Formation) changed from initially submarine to late subaerial indicating growth of edifices above sea level, sea-level rise, or land Subsidence by ca. 50?m. They and the latest Militello volcanics are interlayed with minor shallow-water calcarenites. The Poggio Vina volcanics were submerged during a second sea-level rise amounting to up to 100?m. The sea was generally shallow, i.e., <100?m deep, throughout most of the Late Pliocene and early Pleistocene. The Poggio Vina volcanism took place prior to the Emilian transgression. The sea-level rise might represent a continuation of the subsidence trend that caused the Lower Pliocene Trubi marine basin. Subaerial conditions were reached twice in the approximate time interval 1.9–1.6?Ma during phases of voluminous volcanism that outpaced subsidence. Uplift of approximately 600?m (Palagonia) to 950?m (Monte Lauro) occurred subsequent to emplacement of the Pleistocene alkalic volcanics. Bioclastic carbonates deposited concurrently with uplift drape a major fault scarp east of Palagonia with uplift rates in excess of 0.5?mm/a, provided most uplift occurred during ca. 1?Ma. Basinning continued beneath the half graben of the present Piana di Catania where volcanics several hundreds of meters thick – at least some of them alkalic in composition – occur at a depth of approximately 500–1500?m below the present surface. Quaternary uplift of the northwestern Iblean plateau may have been due to a major phase of underplating or rise of partially melted mantle. Composition of the volcanic rocks, total volume, and mass eruptive rates are well-correlated. The volumetrically very minor highly mafic Messinian nephelinites may have formed in response to Messinian lithosphere unloading following draining of the Mediterranean resulting in very low-degree partial melting. The nephelinitic to basanitic Poggio Inzerillo and Poggio Pizzuto pillow lavas may herald a major mantle decompression event, possibly the rise of a mantle diapir. The remarkably homogeneous bronzite-bearing, relatively SiO2-rich Militello tholeiites, representing a very short-lived but voluminous eruptive phase, resemble E-MORB and reflect a major high-degree partial melting event. The Pleistocene Poggio Vina alkali basalts to nephelinites resemble the late-stage alkalic phase in intraplate magmatic systems. The Iblean cycle of a brief but intense phase of widespread tholeiites followed by alkali basaltic volcanism resembles that of Etna Volcano where widespread basal tholeiites erupted at approximately 0.5?Ma and were followed by (evolved) alkali basaltic lavas. The immediate cause-and-effect relationship between volcanism and tectonism remains speculative.  相似文献   

14.
The cause of the desiccation of the Mediterranean Sea during the Messinian Salinity Crisis has been widely debated, but its re-flooding remains poorly investigated. Interpretations generally involve tectonic collapse of the Strait of Gibraltar or global sea-level rise, or even a combination of both. The dramatic sea-level fall in the Mediterranean has induced deep fluvial incision all around the desiccated basin. We investigate erosion dynamics related to this base level drop by using the numerical simulator EROS. We show that intense regressive erosion develops inevitably in the Gibraltar area eventually inducing the piracy of the Atlantic waters by an eastward-flowing stream and the subsequent re-flooding of the Mediterranean.  相似文献   

15.
Outcrops, offshore wells, electric logs and seismic profiles from northern Tunisia provide an opportunity to decipher the Messinian Salinity Crisis in the Strait of Sicily. Messinian deposits (including gypsum beds) near the Tellian Range reveal two successive subaerial erosional surfaces overlain by breccias and marine Zanclean clays, respectively. In the Gulf of Tunis, Messinian thick evaporites (mostly halite) are strongly eroded by a fluvial canyon infilled with Zanclean clays. The first erosional phase is referred to the intra-Messinian tectonic phase and is analogous to that found in Sicily. The second phase corresponds to the Messinian Erosional Surface that postdates the marginal evaporites, to which the entire Sicilian evaporitic series must refer. The Western and Eastern Mediterranean basins were separated during deposition of the central evaporites.  相似文献   

16.
This study investigates the controls on three-dimensional stratigraphic geometries and facies of shallow-water carbonate depositional sequences. A 15 km2 area of well-exposed Mid to Late Miocene carbonates on the margin of the Níjar Basin of SE Spain was mapped in detail. An attached carbonate platform and atoll developed from a steeply sloping basin margin over a basal topographic unconformity and an offshore dacite dome (Late Miocene). The older strata comprise prograding bioclastic (mollusc and coralline algae) dominated sediments and later Messinian Porites reefs form prograding and downstepping geometries (falling stage systems tract). Seven depositional sequences, their systems tracts and facies have been mapped and dated (using Sr isotopes) to define their morphology, stratigraphic geometries, and palaeo-environments. A relative sea-level curve and isochore maps were constructed for the three Messinian depositional sequences that precede the late Messinian evaporative drawdown of the Mediterranean. The main 3D controls on these depositional sequences are interpreted as being: (i) local, tectonically driven relative sea-level changes; (ii) the morphology of the underlying sequence boundary; (iii) the type of carbonate producers [bioclastic coralline algal and mollusc-dominated sequences accumulated in lows and on slopes of < 14° whereas the Porites reef-dominated sequence accumulated on steep slopes (up to 25°) and shallow-water highs]. Further controls were: (iv) the inherited palaeo-valleys and point-sourced clastics; (v) the amount of clastic sediments; and (vi) erosion during the following sequence boundary development. The stratigraphy is compared with that of adjacent Miocene basins in the western Mediterranean to differentiate local (tectonics, clastic supply, erosion history, carbonate-producing communities) versus regional (climatic, tectonic, palaeogeographic, sea-level) controls.  相似文献   

17.
The Çal Basin formed in the late Miocene as an orogen-top rift hosting terrestrial sedimentation. The initial array of alluvial fans in a half-graben basin was replaced by an axial meandering-river system during the late Tortonian. Palaeomammal taxa indicate a mid-Turolian age of the deposits and a grass-dominated steppe ecosystem. Isotopic data from pedogenic carbonates indicate a warm, semiarid to arid climate. Subhumid to humid climatic conditions prevailed in the Pliocene, with a palustrine environment and savannah-type open ecosystem, recording a regional response to the marine flooding that terminated the Messinian ‘salinity crisis’ in the Mediterranean. Pleistocene saw re-establishment of a fluvial system in the basin with the development of an open steppe ecosystem in warm, semiarid to arid climatic conditions. The sedimentary facies analysis of the basin-fill succession, combined with biostratigraphic data, render the basin a regional reference and help to refine the Neogene tectono-climatic history of SW Anatolia.  相似文献   

18.
A new genetic facies model for deep-water clastic evaporites is presented, based on work carried out on the Messinian Gessoso-solfifera Formation of the northern Apennines during the last 15 years. This model is derived from the most recent siliciclastic turbidite models and describes the downcurrent transformations of a parent flow mainly composed of gypsum clasts. The model allows clearer comprehension of processes controlling the production and deposition of clastic evaporites, representing the most common evaporite facies of the northern Apennines, and the definition of the genetic and stratigraphic relationship with primary shallow-water evaporites formed and preserved in marginal settings. Due to the severe recrystallization processes usually affecting these deposits, petrographic and geochemical analyses are needed for a more accurate interpretation of the large spectrum of recognized gravity-driven deposits ranging from debrisflow to low-density turbidites. Almost all the laminar ‘balatino’ gypsum, previously considered a deep-water primary deposit, is here reinterpreted as the fine-grained product of high to low-density gravity flows. Facies associations permit the framing of the distribution of clastic evaporites into the complex tectonically controlled depositional settings of the Apennine foredeep basin. The Messinian Salinity Crisis occurred during an intense phase of geodynamic reorganization of the Mediterranean area that also produced the fragmentation of the former Miocene Apennine foredeep basin. In this area, primary shallow-water evaporites equivalent to the Mediterranean Lower Evaporites, apparently only formed in semi-closed thrust-top basins like the Vena del Gesso Basin. The subsequent uplift and subaerial exposure of such basins ended the evaporite precipitation and promoted a widespread phase of collapse leading to the resedimentation of the evaporites into deeper basins. Vertical facies sequences of clastic evaporites can be interpreted in terms of the complex interplay between the Messinian tectonic evolution of the Apennine thrust belt and related exhumation–erosional processes. The facies model here proposed could be helpful also for better comprehension of other different depositional and geodynamic contexts; the importance of clastic evaporites deposits has been overlooked in the study of other Mediterranean areas. Based on the Apennine basins experience, it is suggested here that evaporites diffused into the deeper portions of the Mediterranean basin may consist mainly of deep-water resedimented deposits rather than shallow-water to supratidal primary evaporites indicative of a complete basin desiccation.  相似文献   

19.
Spectral analysis of the Messinian Abad marls in the Cariatiz section (Sorbas Basin, south-eastern Spain) reveals three relevant orders of cyclicity. The most significant cycle is in the lowest frequency (average thickness of 365 cm, 4–5 cycles in the section). It is recorded in the composition of planktic foraminiferal assemblages indicative of surface-water temperature, planktic and benthic stable isotope signals, and carbonate proportions. The planktic assemblages, isotope values and carbonate proportions also record a middle-frequency cycle with an average of 177 cm (9–10 cycles in the section). The highest frequency cycle (average of 132 cm, 12–13 cycles in the section) is mainly reflected in siliciclastic and calcite proportions. Age constraints and cycle patterns suggest that the lowest frequency cycle was forced by orbital obliquity, whereas the two higher-frequency ones are related to precession. Obliquity seems to have controlled major changes in surface-water temperature in the Sorbas Basin during the early Messinian. Surface-water temperature was also affected by precession, with changes in weathering and run-off. Spectral analysis has also been applied to vertical shifts of reef facies throughout the progradation of the Cariatiz reef. This reef is coeval with the Cariatiz section. Vertical shifts of reef talus breccias point to the existence of 4–5 major cycles of sea-level change, whereas 7–9 higher-frequency cycles are reflected in the repeated occurrence of lowstand, non-reefal deposits. Correlation with the cycles observed at the Cariatiz section suggests that obliquity forced glacio-eustatic sea-level oscillations in the western Mediterranean during the Late Miocene.  相似文献   

20.
Owing to its expanded stratigraphic sections, the Apennine thrust belt offers the opportunity to better understand the evaporitic and post-evaporitic Messinian events. A physical stratigraphic framework of Messinian deposits, based on facies analysis and basin-wide correlation of key surfaces and sedimentary cycles, is presented. It is shown that the Messinian Apennine foredeep had marginal basins with shallow-water primary evaporites and deeper basins where resedimented evaporites accumulated under relatively deep-water conditions. Like many other Mediterranean examples, primary shallow-water evaporites of Apenninic marginal basins show evidence for subaerial exposure and erosion. However, the development of such an erosional surface does not correspond to the deposition of primary evaporites in the deepest part of the basin(s); here, the unconformity can be traced towards the base of resedimented evaporites or to a level within them, implying that the deeper basins of the Apennine foredeep never underwent desiccation during the Messinian salinity crisis, but rather received the eroded marginal evaporites. This fact, usually overlooked, raises important questions about the deep desiccation model of the Mediterranean.  相似文献   

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